[BUG] Windows Desktop app: `!` interactive shell forces PowerShell, ignoring defaultShell:"bash" (CLI works with identical settings)

Preflight Checklist

• [x] I have searched existing issues. This was reported before in #61516 and #69375, but both were auto-closed by the inactivity/duplicate bot without any fix, and the bug still reproduces on a newer version. The auto-close bot on #61516 explicitly said to open a new issue if still relevant — hence this report.
• [x] This is a single bug report
• [x] I am using the latest version of Claude Code

What's Wrong?

In the Claude Code Desktop app on Windows, the ! interactive shell (and the integrated >_ terminal) always spawns PowerShell, ignoring "defaultShell": "bash" in ~/.claude/settings.json.

The key new data point that the previous reports (#61516, #69375) did not have is an isolation test that proves this is desktop-app-specific, not a configuration problem:

| Run environment | ! shell result |
|---|---|
| Standalone CLI (claude in a terminal), identical settings.json | ✅ Git Bash — !echo $SHELL → /bin/bash.exe |
| Desktop app | ❌ PowerShell — !git branch prints the Windows PowerShell / Copyright (C) Microsoft Corporation banner and runs under powershell.exe |

Same machine, same ~/.claude/settings.json. Since the CLI correctly honors defaultShell: "bash", the settings are valid — the Desktop app simply does not apply defaultShell to its ! interactive shell and falls back to PowerShell.

What Should Happen?

The Desktop app's ! interactive shell (and >_ integrated terminal) should honor "defaultShell": "bash" and use Git Bash, exactly like the CLI does with the same settings.

Steps to Reproduce

1. On Windows with Git for Windows installed, set in ~/.claude/settings.json:

``json
{
"defaultShell": "bash",
"env": {
"CLAUDE_CODE_GIT_BASH_PATH": "C:/Program Files/Git/bin/bash.exe"
}
}
``

1. Fully quit the Desktop app (system tray → Quit) and relaunch.
2. In the Desktop app, run !git branch (or !echo $SHELL).
3. Observe: PowerShell is used (PowerShell banner appears), not Git Bash.
4. For contrast, run claude from a terminal and run the same !echo $SHELL → it correctly returns /bin/bash.exe.

Configuration (relevant settings.json)

{
  "defaultShell": "bash",
  "env": {
    "CLAUDE_CODE_USE_POWERSHELL_TOOL": "0",
    "CLAUDE_CODE_GIT_BASH_PATH": "C:/Program Files/Git/bin/bash.exe"
  }
}

• C:/Program Files/Git/bin/bash.exe exists and bash is on PATH (which bash → /usr/bin/bash).
• defaultShell only accepts "bash" / "powershell" per docs; "bash" is set.
• Fully quit and relaunched the Desktop app; the behavior persists.

Claude Code Version

CLI used for the isolation test: v2.1.196 (!echo $SHELL → /bin/bash.exe, correct). The Desktop app (bundled Claude Code) exhibits the bug.

Operating System

Windows 11 Home (10.0.26200)

Terminal/Shell

Git Bash (Git for Windows) configured as defaultShell; Desktop app forces PowerShell instead.

Additional Information

Related prior reports, both closed without a fix: #61516 (closed NOT_PLANNED / inactivity), #69375 (closed as duplicate of #61516).